This invention relates to apparatus which is a component of end-of-car hydraulic cushioning devices used on railroad cars and a method of repairing such devices. The present invention provides a shaft and piston arrangement for such cushioning devices which facilitates repair should either of these parts become damaged.
End-of-car hydraulic cushioning devices have been used on railroad cars to dampen train action buff and draft forces. Such cushioning devices are known in the art, as represented in U.S. Pat. Nos. 3,589,527 and 3,752,329. The cushioning devices disclosed in these patents, as well as other cushioning devices in use today, utilize a one-piece piston and shaft arrangement to transfer outside coupling forces through a hydraulic fluid-filled housing. As the piston and shaft move through the housing, they displace, hydraulic fluid. The fluid is metered through valves and other orifices in the housing to absorb energy.
Each end-of-car hydraulic cushioning device is designed to fit in a center sill pocket at an end of the railroad car. The shaft includes an end normally provided with a spherical bearing which connects to the car body. The housing is connected to the coupler and is slidable within the sill pocket. The housing has metal stops which engage similar limiting stops fixed on the inside of the sill. These engaging stops limit the length of travel of the housing relative to the piston and shaft as buff and draft forces act upon the railroad car coupler, extending and compressing the cushioning device in its center sill pocket location.
As explained in U.S. Pat. Nos. 4,719,686 and 4,782,740, the disclosures of which are incorporated by reference herein, the cushioning devices are subject to wear which may result in damage to either the piston or shaft, or both. These two patents describe a method and apparatus for repairing a damaged piston and shaft assembly. Specifically, the patents describe how to reuse a piston taken off of a damaged shaft. The method involves the use of a threaded connection between a used piston and a new shaft. Stops are incorporated in the threaded connection to prevent axial movement between the piston and shaft. A threadlock adhesive is used to prevent rotational movement between the parts.